The present disclosure relates generally to automobile steering systems and, more particularly, to a method for automatically adjusting reference models used vehicle stability enhancement systems in response to a change in steering mode.
“Driver's preference” is a feature available in certain electric front controlled, rear controlled or four-wheel automobile steering systems. A drivers preference switch may include settings such as “sporty”, “normal”, “trailering”, “system off”, or other modes representing various vehicle-handling objectives. As a driver changes the preference from one mode to another, a step change in a rear or front steer command could occur. Such a step change, however, may be both noticeable and unacceptable to the driver.
In addition, certain Vehicle Stability Enhancement (VSE) systems currently in existence typically employ a “Reference Model” algorithm that calculates a desirable handling motion for the vehicle. Such reference model algorithms have historically assumed that the desirable handling motion of the vehicle is solely a function of handwheel angle and vehicle speed. However, with the advent of new vehicle systems such as four-wheel steering, rear wheel steering, front controlled steering, active roll control and the like, the desirable handling motion may change when the new system state changes (e.g., as a result of driver preference changes or initial system activation). Thus, the existing reference models are typically not sufficient for use in a VSE system with multiple modes of steering, wherein each steering mode may have different desirable handling responses associated therewith.